The present invention relates to an X-Y stage to be used as index table for an electronic equipment or a precision instrument, and more particularly to an X-Y stage having improved driving means.
A conventional X-Y stage is shown in FIGS. 6 to 8. Referring to FIGS. 6 to 8, an X stage 2 is provided over a fixed plate 1 in such a manner as to be linearly reciprocatively movable through ball bearings B in a horizontal direction, and a Y stage 3 is provided over the X stage 2 in such a manner as to be linearly reciprocatively movable through ball bearings C in a horizontal direction perpendicular to the moving direction of the X stage 2.
A stepping motor 4 is fixed to the fixed plate 1 in such a manner as to project sideward from the X stage 2, and a screw shaft 5 is rotatively driven by the stepping motor 4. The screw shaft 5 is threadedly engaged with a nut (not shown) provided in the X stage 2. Thus, the X stage 2 is reciprocable by driving the stepping motor 4.
Similarly, a stepping motor 6 is fixed to the X stage 2 in such a manner as to project sideward from the Y stage 3, and a screw shaft 7 is rotatively driven by the stepping motor 6. The screw shaft 7 is threadedly engaged with a nut (not shown) provided in the Y stage 3. Thus, the Y stage 3 is reciprocable by driving the stepping motor 6.
In the conventional X-Y stage as mentioned above, the rotary motion of the stepping motor 4 as a driving source is converted into the linear motion through the screw shaft 5 and the nut engaging the same, so as to linearly move the X stage 2, for example. Accordingly, a positioning accuracy of the X stage 2 is limited by backlash of the screw shaft 5 and accumulated error. Further, the X stage 2 cannot be moved at a high speed.
Furthermore, as the stepping motor 4 is so located as to project sideward from the X stage 2, the X-Y stage is enlarged in size.
Additionally, it is very hard to machine a long screw shaft 5 with a high degree of straightness. Accordingly, a moving distance of the X stage 2 is limited.
The above-mentioned problems similarly occur in the Y stage 3.
The present applicant invented a high efficient ultrasonic linear motor utilizing a resonance condition of components (Japanese patent application No. 1-55572). The ultrasonic linear motor is constructed of a traveling member (vibrating member) including at least a pair of leg portions adapted to be vibrated in a direction perpendicular to a rail and a body portion connecting the leg portions and adapted to be vibrated in a direction parallel to the rail. The leg portions and the body portion are vibrated by applying voltages having suitably different phases, so that the motor may on the rail.